1. Field of the Invention
The present invention relates to a near infrared absorption material.
2. Description of the Prior Art
In recent years, development of plasma display panel has been active and its products have been put into market. As is easily anticipated from their principle, plasma display panels emit a near infrared light during the plasma discharge; since this near infrared light is close to the near infrared light used by the remote controllers of electronic appliances such as household TVs, air conditioners, video players and the like, plasma displays invite malfunctioning of the electronic appliances placed in the vicinity thereof. Hence, a near infrared absorption filter is often used as a cover plate of plasma display, for absorption and shielding of a near infrared region of 800 to 1,000 nm, particularly 850 to 1,000 nm.
The above near infrared absorption filter has been produced in various forms. Recently, there has also been proposed a near infrared absorption filter which selectively absorbs not only a near infrared light (absorbed by conventional filters) but also an orange light of 550 to 620 nm wavelength region (this orange light gives an unclear image), but absorbs substantially no visible light of other wavelength region and therefore can give a clear image.
For example, JP-A-2000-250420 and JP-A-2000-275432 each disclose a cover plate for an image display device having a plasma display panel, which is a laminate of a transparent substrate, an antireflection layer, an electromagnetic wave-shielding layer, a near infrared absorption layer and a layer for absorption of 560 to 620 nm wavelength light.
In the cover plate for image display disclosed in JP-A-2000-250420, the layer for absorption of 560 to 620 nm wavelength light is formed by dispersing a dye absorbing such a light, in gelatin. However, since a water-soluble gelatin is used as the gelatin, the coated layer formed shows cissing against a substrate made from a polyethylene terephthalate, polyethylene naphthalate, a polyolefin or the like, making it impossible to obtain a uniform coated layer; moreover, the near infrared absorption dye when added tends to be decomposed in gelatin by heat, humidity or the like and is low in weather resistance and durability. Thus, the cover plate disclosed in the above literature has problems.
The cover plate for image display disclosed in JP-A-2000-275432 is formed by dispersing a dye absorbing 560 to 620 nm wavelength light in a PMMA resin. However, in this case as well, the near infrared absorption dye used tends to be decomposed by heat, humidity or the like and is low in weather resistance and durability. Thus, the cover plate disclosed in the above literature has a problem.
The present invention aims at providing a near infrared absorption material which alleviates the above-mentioned problems of the prior art, which selectively absorbs not only a near infrared light but also an orange light of 550 to 620 nm wavelength region (this orange light gives an unclear image), but absorbs substantially no visible light of other wavelength region and therefore can give a clear image, and which is superior in weather resistance and durability.
According to the resent invention, there is provided a near infrared absorption material comprising:
a transparent substrate, and
at least a transparent resin layer formed thereon, containing a near infrared absorption dye and a dye selectively absorbing a light of 550 to 620 nm wavelength region; or a near infrared absorption material comprising:
a transparent substrate, and
at least a transparent resin layer containing a near infrared absorption dye and an adhesive layer containing a dye selectively absorbing a light of 550 to 620 nm wave-length region, both formed on the transparent substrate so that the adhesive layer becomes the outermost layer.